unfortunately there is not a lot of documentation on customizing toolbars in the ACF WYSIWYG field. What does exist is here https://www.advancedcustomfields.com/resources/customize-the-wysiwyg-toolbars/
You might try one of the results provided in this searh https://www.google.com/search?q=acf+add+controls+to+basic+wysiwyg+field
